SK281033B6 - CONTINUOUS METHOD OF POLYMERIZING OILFINES AND DEVICE FOR IMPLEMENTING THIS METHOD - Google Patents

Abstract

A continuous process for the polymerization of olefins, in particular ethylene, propylene or mixtures of these olefins with other alpha-olefins, in the gas phase in a fluidized bed, in which recycled monomer-containing gas used to agitate said bed is cooled to condense the liquid hydrocarbon. The condensed liquid, which may be a monomer or an inert liquid, is separated from said recycled gas and passed directly. The liquid which is fed to the bed can be passed through spray nozzles with a gaseous spray medium or through liquid nozzles. The apparatus for carrying out the process comprises a reactor (1) with a fluidized bed reactor body (16), fluidized beds (17), a deceleration zone (18), a line (19) connecting the reactor to a cyclone (20), a heat exchanger (21), a compressor (22), a second heat exchanger (23), a separator (24), a line (25) for conducting the recycled liquid and a line (27) for conducting the catalyst or prepolymer to the separated liquid stream.

Description

The invention relates to a continuous process for the polymerization of olefins in a gas phase in a fluidized bed reactor with a higher degree of productivity.

BACKGROUND OF THE INVENTION

Methods of gas phase homopolymerization and copolymerization of olefins are well known in the art. For example, the methods may include introducing a gaseous monomer into a stirred and / or fluidized bed containing a catalyst and a polyolefin already made for polymerization.

In the polymerization of olefins in a fluidized bed reactor, the polymer particles in the bed are maintained in a fluidized state by means of a gas stream which is introduced into the reaction bed and which comprises a gaseous reaction monomer. Typically, a bed containing polymer particles of an already manufactured polymer that is the target of the polymerization is used to initiate the polymerization. During polymer production, catalytic polymerization of said monomer produces fresh polymer which is immediately withdrawn from the bed in order to maintain a more or less constant bed volume. An industrially applicable process utilizes a fluidization grate that distributes the fluidizing gas to the fluidized bed and which at the same time acts as a bed support in the event of a gas supply disruption. The polymer produced is usually withdrawn from the reactor via a discharge line located at the bottom of the reactor near the fluidized bed. Said fluidizing bed comprises a bed of hovering growing polymer particles, polymer product particles, and catalyst parts. The reaction mixture is maintained under fluidization conditions by means of a fluidizing gas stream flowing from the base of the reactor upwards, the gas being composed of recycled gas from the top of the reactor and newly supplied gas.

The fluidizing gas enters the bottom of the reactor and is preferably passed through the fluidized bed to said fluidized bed.

The polymerization of olefins is an exotic reaction and it is therefore necessary to provide said reactor with a means for cooling said bed in order to dissipate the heat generated by the polymerization reaction. In the absence of such cooling, the fluidized bed could raise its temperature to such an extent that the catalyst could be inactivated or the bed could begin to melt. In the polymerization of olefins in said fluidized bed, the preferred method of dissipating the polymerization heat is a process wherein gas is introduced into the reactor, preferably a fluidization gas having a temperature below the desired polymerization temperature and passed through said fluidized bed to remove polymerization heat. , then discharged from said reactor, cooled in an external heat exchanger and recycled back to said bed. The temperature of said recycle gas can be adjusted in a heat exchanger in order to maintain the fluidization bed at the desired polymerization temperature. In this alpha olefin polymerization process, said recycle gas typically comprises said monomeric olefin, optionally together with a diluent gas or gas transfer agent such as hydrogen. Thus, said recycle gas serves to deliver said monomer to the fluidized bed and bring the fluidized bed to the desired temperature. The monomers consumed by the polymerization reaction are usually replaced by adding fresh gas to the recycle gas stream.

It is well known that the production rate (i.e., reactor power or productivity - product weight per unit time and unit volume) in commercial fluidized bed gas reactors of the above type is limited by the maximum rate at which polymerization heat can be removed from the reactor. This rate of heat removal can be increased, for example, by increasing the rate of said recycle gas and / or lowering its temperature. But this rate is limited to the rate of recycle gas that can be used in commercial practice. When this limit is exceeded, said bed may become unstable or even be discharged out of the reactor in a stream of said gas, which could lead to clogging of said recycling line and failure of the compressor or fan of said recycling gas. Another limitation is the practical possibility of cooling said recycle gas. This limitation is primarily determined by the requirements and, in practice, is usually determined by the temperature of the industrial chilled water available at the plant. Cooling can be used if desired, but this increases production costs. Thus, in commercial practice, the disadvantage of using cooled recycled gas as the only means to remove the polymerization heat from the fluidized bed in the gas phase polymerization of olefins is to limit the maximum production rate.

The prior art offers a variety of methods for dissipating the polymerization heat produced by gas-phase polymerization in a fluidized bed.

GB 1415442 relates to a gas phase polymerization of vinyl chloride in a stirred or fluidized bed reactor which is carried out in the presence of a single gas diluent having a boiling point lower than the boiling point of vinyl chloride. Example 1 of this document describes the control of the polymerization temperature by intermittent addition of liquid vinyl chloride to the fluidized polyvinyl chloride material. This liquid vinyl chloride is immediately evaporated in the fluidized bed, resulting in the dissipation of polymerization heat.

US 3625932 describes a process for the polymerization of vinyl chloride in which the beds of polyvinyl chloride particles in a multi-stage fluidized bed reactor are kept in a fluidized state by introducing gaseous vinyl chloride monomer through the bottom of said reactor. Cooling of each bed to remove the polymerization heat generated in the bed is accomplished by injecting liquid vinyl chloride monomer into the feed gas stream below the fluidized bed.

FR 22155802 relates to a valve spray nozzle suitable for injecting liquids into fluidized beds, for example in the gas polymerization of ethylenically unsaturated monomers in a fluidized bed. The fluid used to cool the bed may be a monomer to be polymerized or, if ethylene is to be polymerized, it may be a liquid unsaturated hydrocarbon. Said spray nozzle is described in connection with the fluidized bed polymerization of vinyl chloride.

GB 1398965 describes the fluidized bed polymerization of ethylenically unsaturated monomers, in particular vinyl chloride, in which the thermal control of the polymerization is ensured by injecting liquid monomer into said bed using one or more injection nozzles positioned at 0 to 75% of the height of fluidized bed fluidized bed. reactor.

US 4390669 relates to the homopolymerization or copolymerization of olefins carried out in a multi-stage gas-phase polymerization process which can be carried out in stirred-bed reactors,

Fluidized bed, stirred fluidized bed reactors or cylindrical reactors. In this method, the polymer obtained from the first polymerization zone is suspended in the central zone in a slightly volatile liquid hydrocarbon and the suspension thus obtained is introduced into a second polymerization zone in which the liquid hydrocarbon is evaporated. In Examples 1 to 5, the gas from said second polymerization zone is conveyed through a condenser (heat exchanger) in which a portion of said liquid hydrocarbon condenses (with a comonomer if used). Said volatile liquid condensate is partially deposited in the liquid state in a polymerization vessel in which it evaporates and thus dissipates the heat generated by the latent heat of polymerization. This specification does not deal with a specific method of introducing a liquid into said polymerization.

EP 89691 relates to a process for increasing reactor productivity in continuous gas phase fluidized bed polymerization of liquid monomers in a fluidized bed, the process comprising a cooling portion so that all unreacted fluids form a biphasic gas / feed mixture below the dew point and re-introduce the biphasic mixture to the reactor. This technique is referred to as a "condensation mode" operation. This patent discloses that the primary limitation of the cooling of the recycle gas stream below the dew point is to maintain the gas to liquid ratio to be sufficient to maintain the liquid phase of the biphasic liquid mixture under the inlet conditions until the liquid evaporates. It also states that the amount of liquid in the gas phase should not exceed about 20 weight percent and preferably should not exceed about 10 weight percent, provided that the rate of said two-phase recycle stream is high enough to maintain the liquid phase in suspension in said gas. and carrying a fluidized bed in said reactor. EP 89691 further discloses that it is possible to produce a biphasic fluid stream inside the reactor, wherein the gas and liquid are injected separately into the reactor at the injection site under conditions that allow the biphasic flow to occur, but nevertheless the advantage of the process is not too great that the subsequent separation of the gaseous and liquid phases after cooling increases the cost of this polymerization process.

In particular, EP173261 relates to improvements in the distribution of the fluid lifted into a fluidized bed reactor, and in particular it relates to the operation in the condensation mode described in EP89691. This patent discloses that operation using an inlet in the reactor base (below a distribution plate or grate) of a standing tubular / conical type (shown in the figures of EP 89691) is not sufficient to operate in a condensation mode, for example due to flooding of the bottom. . This phenomenon can be found in commercial reactors at relatively low proportions of liquid in the recycle stream.

It has now been found that by cooling the recycled gas stream to a temperature sufficient to form a liquid and a gas and separating the liquid from the gas and then introducing said liquid directly into said fluidized bed, the total amount of liquid that can be introduced into the fluidized bed of the polymerization reactor cooling the bed due to evaporation of said liquid to increase the cooling level and thereby achieve higher productivity.

Thus, the invention provides a continuous process for the polymerization of an olefin monomer selected from the group consisting of (a) ethylene, (b) propylene, (c) mixtures of propylene and ethylene, and (d) mixtures of a, b or c with one or more other alpha-olefins in the gas phase. a fluidized bed reactor comprising continuously recycling a gas stream comprising at least some ethylene and / or propylene through a fluidized bed in said reactor in the presence of a polymerization catalyst under reaction conditions, wherein at least a portion of said gas stream withdrawn from said reactor is cooled to wherein said liquid condenses, separating at least a portion of the condensed liquid from said gaseous stream and introducing at least a portion of the separated liquid directly into said fluidized bed at a location where said gaseous stream passing through said fluidized bed substantially reaches a gaseous stream temperature is withdrawn from or above said reactor.

Said recycle gas stream withdrawn from said reactor (hereinafter referred to as "unreacted fluids") comprises unreacted gaseous monomers and optionally inert hydrocarbons, reaction activators or moderators as well as a feed catalyst and polymer particles.

Said recycle gas stream fed to said reactor further comprises a sufficient amount of fresh monomers to replace the monomers that have been polymerized in said reactor.

The process of the invention is suitable for the production of gas phase polyolefins in which one or more olefins are polymerized, at least one of which is ethylene or propylene. Preferred alpha-olefins useful in the process of the invention are alpha-olefins having 3 to 8 carbon atoms. However, if desired, minor amounts of alpha-olefins having more than 8 carbon atoms, for example 9 to 18 carbon atoms, may also be used. Thus, homopolymers of ethylene or propylene or copolymers of ethylene or propylene with one or more alpha-olefins having 3 to 8 carbon atoms can be produced. Preferred alpha-olefins are but-1-ene, pent-1-ene, hex-1-ene, 4-methylpen-1-ene, oct-1-ene and butadiene. Examples of higher olefins that can skopolymerizovať with the primary ethylene or propylene monomer, that is to act as a partial substitute C ₃ -C ₈ monomer are dec-l-ene and eetilidénnorbomén.

When used to copolymerize ethylene or propylene with alpha-olefins, ethylene or propylene is present as a major component of said copolymer and is preferably present in an amount of at least 70% of all monomers.

The process of the invention can be used to produce a variety of polymer products, such as linear low density polyethylene (LLDPE), based on copolymers of ethylene with butane, 4-methylpent-1-ene or hexene, and high density polyethylene (HDPE), which may be homopolyethylene. or copolymers of ethylene with a small portion of a higher alpha-olefin, for example butene, pent-1-ene, hex-1-ene or 4-methylpent-1-ene.

The liquid that condenses from the recycled gas stream may be a liquefiable monomer, such as butene, hexene, octene, used as a comonomer in the production of LLDPE, or the liquid may be an inert liquefiable liquid, such as butane, pentane, hexane.

It is important to use a fluid that will evaporate in said fluidized bed under polymerization conditions so as to achieve the desired cooling effect and substantially eliminate the accumulation of fluid within said bed. Suitably, at least 95%, preferably at least 98% by weight and most preferably substantially all of the liquid supplied to said bed evaporates in said fluidized bed. In the case of liquid comonomers, a portion of the comonomer polymerizes in said bed, whereby both the liquid phase and the gas phase can be used for the polymerization. As is well known with respect to conventional gas phase polymerization or non-polymerization processes, a small portion of said monomer (and comonomer, if any) tends to remain (absorbed or dissolved) in the polymer product until the polymer is subjected subsequent degassing. This amount or even a higher amount of absorbed or dissolved monomer / comonomer can be easily tolerated in said bed, provided that this amount does not adversely affect the fluidizing properties of said bed.

The process is particularly suitable for the polymerization of olefins at a pressure of between 0.5 and 6 MPa and a temperature of between 30 ° C and 130 ° C. For example, in the production of LLDPE, the temperature is suitably in the range of 80 to 90 ° C, and in the manufacture of HDPE the typical temperature is usually in the range of 85 to 105 ° C, depending on the efficiency of the catalyst used.

Said poylmerization reaction may be carried out in the presence of a Ziegler-Natta type catalyst system comprising a solid catalyst essentially consisting of a transition metal compound and a cocatalyst consisting of an organic metal compound (i.e., an organometallic compound, for example an alkylaluminium compound). High-performance catalyst systems have been known for many years and are capable of producing large quantities of polymer in a relatively short time, and this makes it possible to eliminate residue removal from said polymer. These highly efficient catalyst systems typically include a solid catalyst consisting essentially of transition metal, magnesium, and halogen atoms. It is also possible to use a highly active catalyst consisting essentially of heat activated chromium trioxide and coupled to a refractory oxide granular carrier. The use of this process is also suitable when using silica supported metallocene catalysts and Ziegler catalysts.

The advantage of this process according to the invention is that the improved cooling effect is of considerable benefit in particular to polymerization processes using highly active catalysts, such as metallocene catalysts.

Said catalyst may conveniently be used in the form of a prepolymerized powder prepared during the prepolymerization stage using said catalyst. This prepolymerization can be carried out by any suitable method, for example by polymerization in a liquid hydrocarbon diluent or in a gas phase using a batch process of the semi-continuous process or a continuous process.

In a preferred method of the invention, substantially all of the recycled gas stream is cooled and separated and all of the separated liquid is introduced into the fluidized bed.

In an alternative embodiment of the invention, the recycle gas stream is divided into a first stream and a second stream. Said first stream is routed directly to said reactor in a conventional manner by injection under said fluidization grid and the second stream is cooled and divided into a gas stream and a liquid stream. Said gas stream may be returned to said first stream and reintroduced into said reactor below said bed, for example under said fluidizing grate, if used. Said separated liquid is introduced into said fluidized bed by the method of the invention.

Said stream of recycled material is suitably cooled by means of a heat exchanger or exchanger to a temperature at which said liquid is liquefied in said gas stream. Suitable heat exchangers are well known in the art.

Said gaseous stream exiting the reactor through its upper portion can carry a quantity of catalyst and flowing particles and these can, if desired, be removed from the recycle gas stream by means of a cyclone. A small fraction of these particles or fines may remain in the recycle gas stream, and after cooling and separation of the liquid from said gas, the fines may, if desired, be reintroduced into said fluidized bed along with a separate liquid stream.

Said recycle gas stream may also include inert hydrocarbons used to inject said catalyst, reaction activators and moderators into said reactor.

Fresh monomers, such as ethylene, to replace the monomers consumed by the polymerization reaction can be added to the recycle gas stream at any convenient location.

Liquidable monomers, for example butene, hexene, 4-methylpent-1-ene and octene, which can be used, for example, as comonomers for the production of LLDPE or inert liquefied liquids, for example pentane, isopentane, butane or hexane, can be introduced as liquids.

For example, inert liquids such as pentane may be injected into the recycle gas stream between the heat exchanger and the separator. In the manufacture of LLDPE, if desired, said comonomer, for example butene, may be injected into the recycled gas stream before it enters said heat exchanger.

Suitable means of separating said liquid are, for example, a cyclone separator, large vessels that reduce the gas flow velocity for efficient separation (knock-off rollers), a gas separator and a demister and liquid scrubber liquid, such as a Venturi scrubber. Such separators are well known in the art.

The use of a demister-type liquid and gas separator is particularly preferred for the purposes of the method of the invention. It is preferable, in respect of the recycled gas stream, to precede the said gas and liquid separator with a cyclone separator. This separates from the gas stream leaving the reactor a major portion of the fines, thereby facilitating the work of the demisting separator and also reduces the possibility of fouling of said separator, resulting in a much more efficient operation.

Another advantage of using a demister type separator is that the pressure drop inside said separator can be lower than in the other types of separator, which increases the efficiency of the overall process.

A very suitable demister for use in the method of the invention is a commercially available vertical gas separator known as "Peerless" (type DPV P8X). This type of separator operates on the principle of liquid droplet combining on a paddle arrangement in order to separate said liquid from said gas. The bottom of the separator is equipped with a large liquid reservoir designed to collect liquid. Said liquid reservoir allows said liquid to be stored and thereby provides control over the discharge of said liquid from the separator. This type of separator is very efficient and provides substantially 100 separation of condensed liquid from said gas stream.

If desired, said liquid reservoir of said separator may be equipped with a filter screen or other suitable means to collect any fines that remain in said separated liquid.

Said separated liquid is suitably introduced into said fluidized bed at a location where said recycled gas stream is introduced into said reactor in a fluidized bed.

In principle, the temperature of the recycle gas stream being withdrawn reaches or exceeds the temperature of said reactor. The introduction of said separated liquid into said reactor can be carried out at several points in the space of said fluidized bed, which may be at different heights of the fluidized bed. Said site or sites through which the liquid is introduced are arranged such that the local concentration of the liquid introduced does not adversely affect the swirling of said fluidized bed or the quality of said product so as to allow rapid dispersion of the liquid from each site and evaporation in said bed. removal of polymerization heat resulting from the external reaction. In this method of introducing a quantity of liquid for cooling purposes, it is much closer to said maximum filling, which can be tolerated without disturbing the swirl properties of said bed and thus offers the possibility of achieving increased productivity of said reactor.

Said liquid may, if desired, be introduced into said fluidized bed at different heights of the bed. This technique can facilitate increased control over the incorporation of comonomers. Controlled introduction into said fluidized bed provides additional useful control over the temperature profile of said bed and, when said liquid comprises a comonomer, provides useful control over the incorporation of said comonomer into said copolymer.

Preferably, said liquid is introduced into the lower portion of said fluidized bed region in which said recycled gas stream substantially reaches the temperature of the gas stream withdrawn from said reactor. Commercial processes for the polymerization of olefins in a gas fluidized bed are usually conducted under substantially isothermal steady state conditions. However, although at least a major portion of said fluidized bed is maintained at the desired substantially isothermal polymerization temperature, there is usually a temperature gradient in the region of said bed immediately above the point of introduction of said cooled recycled gas stream into said bed. The lower temperature limit in the region of said temperature gradient is the temperature of said incoming cold recycled gas stream and the upper limit is essentially the isothermal temperature of the bed. In commercial fluidized bed type reactors, this temperature gradient is normally located in a layer of about 115 to 30 cm (6 to 12 inches) above the bed.

In order to achieve maximum successful cooling of said separated liquid, it is important that said liquid is introduced into said bed above the region of said temperature gradient, i. j. in a portion of the bed that substantially reaches the temperature of the gas stream leaving the reactor.

The points or points of introduction of said liquid into said fluidized bed may be, for example, approximately 50 to 70 cm above said fluidized bed.

In practice, the process according to the invention can be carried out, for example, by first determining the temperature profile inside said fluidized bed during polymerization, for example by using thermocouples placed in or on the walls of said reactor. Said point or points of introduction of said liquid are then arranged to ensure that said liquid enters an area of said bed where said recycled gas stream substantially reaches the temperature of said gas stream which is withdrawn from said reactor.

Figure 1 represents the temperature profile inside a typical fluidized bed reactor suitable for gas phase polymerization of olefins.

Said temperature profile (Figure 1a) is characteristic of the fluidized bed used to prepare HDPE, where the yield is 23.7 tonnes / hour. Said temperatures were measured using thermocouples placed on the walls of said reactor at locations corresponding to different positions (1-5) inside the fluidized bed. These positions 1-5 within said fluidized bed are shown in Figure 1B.

The temperature profile and the graph show: the level of the fluidization grid (A) and the top of the fluidized bed (B). Said temperature gradient is evident in the region between position 1 and position 3. The region in which said recycled gas stream substantially reaches the temperature of the unreacted fluids leaving said reactor is shown as the region between position 3 and position 5. This is the area for introducing said separating the liquid into said fluidized bed using the method of the invention.

Said liquid is preferably introduced into said fluidized bed at said bottom thereof, i. j. just above position 3 of the temperature profile in Figure 1A.

By increasing the amount of liquid that can be introduced into said fluidized bed and thereby increasing the cooling capacity of the system, higher productivity of said polymerization reactor can be achieved. Compared to other polymerization processes carried out in a fluidized bed in the gas phase, the specific power of the reactor can thus be increased. A further advantage of the method according to the invention is that, due to the separate introduction of said liquid into said fluidized bed, an accurate measuring means can be used to control the supply of the liquid into the bed. This technique facilitates improved cooling control and provides improved control over the transport of any liquid comonomer delivered in this manner to said bed. Thus, the method of the invention may operate in a manner that is not dependent, for example, on any need to maintain the fluid entrained by said cyclized gas stream. As a result, the amount of liquid supplied to said bed can be varied in a much wider range than hitherto. For example, improved control of the comonomer feed or inert gases added to said bed may be used to control the density of the polymer produced and the specific power of said polymerization reactor.

It is important to ensure that the temperature in said fluidized bed is maintained at a temperature below the sintering temperature of said polyolefin constituting said bed.

The gas removed from said scrubber is recycled to said bed, usually through the bottom of said reactor. When a fluidization grate is used, this recycle gas is usually introduced into the area below said grate and said grate facilitates uniform distribution of said gas in order to swirl said fluidized bed. The use of said fluidizing grid is preferred. Fluidization grates that are suitable for the purposes of the method of the invention may be conventional, for example, flat or plate plates perforated by a plurality of holes spaced more or less evenly over their surface. The openings may, for example, have a diameter of approximately 5 mm.

The method of the invention operates at a gas velocity in said fluidized bed which must be greater than or equal to the velocity required to swirl said bed. The minimum gas velocity is usually about 6 cm / s, but the process of the invention is preferably carried out using a velocity of 40 to 100, preferably 50 to 70 cm / s.

SK 281033 Β6

In the process of the invention, if desired, said catalyst or prepolymer may be introduced into said fluidized bed directly with a stream of said separated liquid. This technique may lead to improved dispersion of said catalyst or prepolymer in said bed.

If desired, liquid or liquid-soluble additives, for example, activators, cocatalysts and the like, may be added to said bed together with the liquefied liquid by the method of the invention.

When the process of the invention is used to produce ethylene homopolymers or copolymers, preferably fresh ethylene, for example ethylene, to replace the ethylene consumed during polymerization, may be introduced into said scrubbing gas stream prior to introduction into said bed (e.g. under a fluidizing bed). grate, if applicable). By adding fresh ethylene to the stream of said scrubbing gas and not to the recycled gas stream prior to scrubbing, the amount of liquid that can be isolated from said scrubber and, as a result, the polymerization productivity can be increased.

Said stream of separated liquid may be subjected to further cooling (for example using known cooling techniques) before being introduced into said fluidized bed. This additional cooling makes it possible to achieve an even greater cooling effect in said fluidized bed than in the case where cooling only provides evaporation alone (latent heat of ignition) and thus a further potential increase in the polymerization productivity of the invention. Cooling of the stream of said separated liquid can be achieved by the use of suitable cooling means, for example a simple heat exchanger or cooler located between said separator and said reactor. A further advantage of this feature of the invention is that by cooling said liquid prior to introduction into the fluidized bed, it also reduces the possibility that said catalyst or prepolymer that may be present in said fluid stream does not polymerize prior to introduction into the fluidized bed.

Said liquid may be introduced into said fluidized bed by suitably arranged injection means. Only one injection means or a plurality of injection means suitably arranged in the fluidized bed may be used to inject liquid into the fluidized bed. In a preferred embodiment, the plurality of injection means is substantially uniformly distributed in the region of the fluidized bed defined for introducing said liquid. The number of injection means used is that necessary to provide sufficient penetration and dispersion of liquid in each injection means in order to achieve good liquid dispersion in said bed. The preferred number of injection means is four.

Separate liquid may be supplied to each injection means, if desired, by means of a common pipe suitably arranged in said reactor. Such a pipeline may, for example, be a pipeline extending upward through the center of said reactor.

Said injection means are preferably arranged so as to extend substantially vertically into said bed, but may also be arranged such that they project from the walls of said reactor in a substantially horizontal direction.

The rate at which the liquid may be introduced into the bed depends primarily on the desired degree of cooling in said bed and this in turn depends on the desired rate of production in said bed. The production rates of the polymers obtainable using commercial fluidized bed olefin polymerization processes depend inter alia on the efficiency of the catalysts used and the kinetics of the catalysts. Thus, for example, if catalysts of very high efficiency are used and very high production rates are desired, the rate of addition of the liquid will also be high. Typical liquid introduction rates may be, for example, 0.3 to 4.9 meters of cubic of said liquid per meter of cubic bed material per hour, or even higher.

Preliminary Ziegler catalysts of the "super-efficient" type (i.e., those based on transition metal, magnesium halide and organometallic cocatalyst), the liquid may be introduced into the bed at a rate of 0.5 to 1.5 meters of cubic liquid per meter of cubic bed material per hour.

In the process according to the invention, the weight ratio of liquid to total gas which can be introduced into said bed can be, for example, in the range 1: 100 to 2: 1, preferably in the range 5: 100 to 85: 100, most preferably in the range 6: 100 to 25: 100. By total gas is meant a gas that is returned to the reactor to swirl the fluidized bed together with any gas that can be used as an auxiliary gas for the operation of said injection means, for example a sputter gas.

Injecting a liquid into said fluidized bed in this method may be useful for the catalyst present in said liquid due to the localized cooling effect of the penetrating liquid surrounding the individual injection means, which may prevent hot spots and consequently agglomerations.

Any other suitable injection means can be used to penetrate and disperse the liquid into the fluidized bed, which allows good liquid dispersion in the bed to be achieved.

A preferred injection means is a nozzle or a plurality of nozzles which include spray nozzles with a gaseous spray medium in which a gas or only liquid spray nozzles is used as a liquid spray auxiliary.

The invention further provides a continuous process for the polymerization of an olefin monomer selected from the group consisting of (a) ethylene, (b) propylene, (c) a mixture of ethylene and propylene, and (d) a mixture of a, b or c with one or more other alpha-olefins. a fluidized bed characterized in that it continuously recycles a gas stream comprising at least some ethylene and / or propylene through a fluidized bed in said reactor in the presence of a polymerization catalyst under reaction conditions, wherein at least a portion of said gas stream withdrawn from said reactor is cooled to a temperature; wherein said liquid condenses to include separating at least the condensed liquid from the gas stream and introducing it directly into said fluidized bed by one or more liquid or spray nozzles with a gaseous spray medium. Said fluidized bed is preferably supported above the fluidizing grid.

Suitably, the injection means are nozzles which are introduced into said fluidized bed through the walls of said reactor (or through a grate) and which have one or more nozzle outlet openings for conveying said liquid into the fluidized bed.

Important in the method of the invention is to achieve good dispersion and penetration of the liquid in said bed. The factors which are important for achieving good penetration and dispersion are the motive force and direction in which the liquid is introduced into the bed, the number of places where the liquid is introduced into the bed relative to the unit of the cutting surface of the bed and the spatial arrangement of these insertion points. .

SK 281033 Β6

According to another feature, the invention further provides a process for the polymerization of an olefin monomer, preferably selected from the group consisting of (a) ethylene, (b) propylene, (c) a mixture of ethylene and propylene, and (d) a mixture with, b or c with one or more other alpha -olefins in a fluidized bed reactor characterized by the continuous recycling of a gas stream comprising at least some ethylene and / or propylene through a fluidized bed in said reactor in the presence of a polymerization catalyst under reaction conditions, wherein at least a portion of said gas stream withdrawn from said reactor is cooled a temperature at which said liquid condenses by separating at least a portion of the condensed liquid from said gaseous stream and introducing at least a portion of the separated liquid directly into said fluidized bed at a point where said gaseous stream passing through said fluidized bed substantially reaches a temperature a gaseous stream being withdrawn from or above said reactor, said liquid being introduced into said reactor as one or more streams of liquid alone or one or more streams of liquid and gas through one or more nozzle outlets, and the individual streams having a horizontal flow rate momentum in the case of only a liquid nozzle of at least 100 x 10 ³ kg. s ''. m ^-2 xx M.s ' ¹ and in the case of gas-liquid nozzles 200 kg.s''. m · ² xx M.s' ¹ , said horizontal flow momentum being defined as the liquid flow rate (kilograms per second) in the horizontal direction per unit of cutting area (square meters) of the nozzle exit orifice from which the liquid is ejected, multiplied by the horizontal velocity component (meters per second) of that nozzle.

Preferably, the inlet momentum of the individual liquid or liquid-gas streams is at least 250 x 10 ³ and most preferably at least 300 x 10 ³ kg · s · m · ² × m · s ^-1 . It is particularly preferred to use a horizontal flow momentum in the range of 300 x 10 ³ to 500 x 10 ³ kg · s · m · ² x ms ^-1 . In the case where the liquid jet is ejected from said nozzle outlet in a direction other than horizontal, the horizontal component of the velocity of said jet is calculated from cosine Q ° x the current jet velocity, where Q ° is the angle that said jet flows with the horizontal .

The direction of movement of the one or more liquid streams or liquid-gas streams introduced into said fluidized bed is preferably substantially horizontal. When one or more nozzle outlet orifices transport liquid or liquid-gas streams in a direction other than the horizontal direction, the streams preferably enclose an angle less than 45 °, most preferably less than 20 °, with the horizontal.

Said one or more nozzles are provided with one or more nozzle outlets. The number of nozzles and the number and distribution of said nozzle outlets are important factors for achieving good fluid distribution in said fluidized bed. When a plurality of nozzles are used, these nozzles are preferably vertically spaced and horizontally spaced substantially uniformly from each other. In this case, said apertures are also preferably equally spaced from one another and are equidistant from the vertical wall of said fluidized bed. The number of nozzles per 10 square meters of horizontal cross-section of said bed is preferably 1 to 4, most preferably 2 to 3. If the number is not an integer, then it is preferable to round it to an integer. The number of nozzle outlets at each nozzle is preferably from 1 to 40, most preferably from 3 to 16. If said nozzle comprises more than one nozzle outlet, then said outlet holes are preferably arranged circumferentially around said nozzle at regular intervals.

As already mentioned, said liquid streams may be entirely liquid or may be a liquid-gas mixture stream. Such gas may only be entrained in said liquid, or may be used to atomize said liquid, or as a driving force to drive said liquid.

A suitable spray nozzle with a spray gas medium which can be used for the purposes of the process according to the invention has:

(a) at least one fuel inlet port, (b) at least one atomizing gas inlet port, (c) a mixing chamber for mixing said liquid and gas, and (d) at least one inlet port through which said mixture is discharged.

The sputter gas may suitably be, for example, an inert gas, for example nitrogen, but preferably fresh ethylene. Each nozzle may be provided with a plurality of outlet openings of a suitable configuration. Said discharge openings may be, for example, circular openings, slots, ellipsoids or other suitable configurations. Each nozzle may include a plurality of discharge orifices with different configurations.

The size of the orifices is preferably of a size that provides a small pressure drop across the orifices.

Said discharge openings are preferably arranged symmetrically around the periphery of each nozzle, but may also be arranged asymmetrically.

Said spray gas supplied to the individual nozzles is maintained at a pressure sufficient to disperse said liquid into small droplets and prevent particles from entering said fluidized bed into the orifices of the nozzles and clog them. >

The relative size of said mixing chamber is selected to ensure optimal atomization. The volume of said mixing chamber (spray chamber) relative to the volume of liquid passing through said chamber, expressed as: The volume of the mixing chamber (in cubic centimeters) / liquid flow rate (cubic centimeters per second) is preferably in the range of 5 x 10 ' ³ to 5 x 10 ¹ sec.

The liquid velocity is preferably maintained at a value sufficient to ensure that no particles, such as a fine fraction, are separated from said liquid stream.

The proportion by weight of the atomizing gas to the liquid supplied to each nozzle is usually in the range of 5:95 to 25:75.

Figure 2 shows a nozzle that can be suitably used in the method of the invention.

In the figure, the nozzle comprises a cover 7 having an upper part 8 and a lower part 9. Said upper part is provided with a number of outlet openings 10 arranged on its periphery and a mixing chamber 11 inside this part. Said lower part is provided with a centrally located conduit 12 opening into said mixing chamber and an outer conduit 13 arranged around said inner conduit 12. Said conduit 13 communicates with said mixing chamber through suitably arranged apertures 14. The pressurized liquid is introduced into said nozzle via conduit 13 and atomizing gas is introduced into said nozzle via line 12. The lower portion of said nozzle 9 is connected by conventional means to the supply of pressurized liquid and atomizing gas. After mixing with said gas in the chamber 11, said liquid is discharged from said nozzle through the discharge orifices 10 as a spray spray.

A preferred spray nozzle with a gaseous spray medium is a nozzle, the discharge openings of which are formed by a series of substantially horizontal slots arranged around the periphery of said nozzle. The nozzle may also include a vertically oriented orifice positioned so that the pressurized liquid-gas mixture can remove any particles adhering to the top of the nozzle.

The slots may typically be of a size identical to a hole diameter of about 6.5 mm and may, for example, have a diameter of 0.75 mm x 3.5

Said injection means may alternatively comprise only a liquid spray nozzle or nozzles. Suitably, only the liquid spray nozzle which can be used in the method of the invention comprises at least one inlet port for pressurized liquid and at least one outlet port for the pressurized liquid, while maintaining said liquid at a pressure inside said nozzle sufficient to provide the desired inflow momentum of the liquid discharged from said discharge opening.

The pressure drop in each nozzle can be controlled if necessary, for example by means of restrictive devices such as valves.

Said discharge openings may have a similar configuration to the discharge openings already defined for the atomizing gas spray nozzles. A preferred configuration for said liquid spray nozzle orifices is a circular orifice orifices. The diameter of said apertures preferably ranges from 0.5 to 5.00 mm, most preferably from 0.5 to 2.5 mm.

The droplet size of said liquid is influenced by a number of factors, in particular in spray nozzles with a gaseous spray medium, the ratio of said liquid to the spray gas supplied to said nozzle, and the size and configuration of said spray chamber. The required droplet size for a spray nozzle with a gaseous spray medium is about 50 to 1000 microns. In the case of liquid spray nozzles, the droplet size of said liquid is influenced in particular by the pressure drop in said nozzle and the size and configuration of said discharge openings. The desired droplet size of the liquid for the liquid spray nozzle is approximately 2000 to 4000 microns. Such droplets can be generated, for example, by disrupting the liquid stream by moving the solid particles in said fluidized bed.

The pressure drop for both types of nozzles must be sufficient to prevent particles from entering said fluidized bed into said nozzle. Suitably the pressure drop in the spray nozzle with the gaseous spray medium is 0.2 to 0.7 MPa, preferably 0.3 to 0.5 MPa and in the liquid spray nozzles it is 0.2 to 0.7 MPa and preferably 0.4 to 0.7 MPa. 0.5 MPa.

Should the supply of liquid and / or spray gas to both types of nozzles be interrupted, suitable emergency means for introducing the scrubbing gas will prevent the nozzle from clogging due to the ingress of solid particles from the fluidized bed into the nozzle with a suitable scrubbing gas. is nitrogen. It is important that the size of said spray orifice orifices with gaseous spray media or liquid nozzles only is sufficient to allow passage of all fine particles that may be present in the liquid stream.

In both types of nozzles, said discharge openings can be arranged at different heights of each nozzle. These outlet openings can, for example, be arranged in series of rows.

The type of nozzle shown in Figure 2 preferably has 4 to 20 discharge openings on each nozzle, for example 20 to 20

40, most preferably 4 to 16. The diameter of the nozzle is also preferably 4 to 30 cm, for example 10 to 30 cm, and most preferably about 7 to 12 cm.

Other types of nozzles, for example supersonic nozzles, can also be used in the method of the invention.

Before the liquid is introduced into the polymerization reactor using the polymerization process of the present invention carried out in said fluidized bed, said polymerization process may be initiated in a conventional manner, for example by feeding said bed with particles of the appropriate polymer and subsequently initiating gas flow through the fluidized bed.

If appropriate, said liquid may be introduced into said bed, for example by means of said injection means.

The methods of the invention will now be described with reference to the accompanying drawings.

Figures 3 to 5 schematically illustrate the methods of the invention.

Figure 3 shows a fluidized bed gas phase reactor comprising essentially a reactor body 15, which is typically a upright cylinder having a fluidizing grid 16 disposed in its base. The reactor body comprises a fluidized bed and a velocity-retarding zone 18, which is typically of greater cross-section compared to said fluidized bed.

Said gaseous reaction mixture leaving the top of the reactor fluidized bed constitutes a recycled gas stream and passes through line 19 to cyclone 20 to separate most of the fine particles. The separated fine particles may suitably be returned to said fluidized bed. Said recycled gas stream leaving the cyclone enters the first heat exchanger 21 and the compressor 22. The purpose of the second heat exchanger 23 is to dissipate the heat generated by the compression after said recycled gas stream passes through said compressor 22.

The heat exchanger (s) may be arranged either upstream or downstream of said compressor 22.

After cooling and pressing to the condensate forming temperature, the resulting gas-liquid mixture passes to a separator 24 where the liquid is separated.

The gas leaving said separator is recycled through line 25 to the bottom of said reactor 15. The gas is passed through fluidization grid 16 to said bed, ensuring that said bed remains whirled all the time.

Said separated liquid is led from said separator 24 via line 25 to a reactor 15. If necessary, a pump 26 may be suitably placed in line 25.

The catalyst or prepolymer is passed through line 27 into the stream of liquid to be separated and into the reactor. The polymers produced can be suitably removed from the reactor via line 28.

The arrangement shown in Figure 3 is particularly suitable for use on existing polymerization reactors for introducing gas phase polymerization in a fluidized bed.

Figure 4 shows an alternative arrangement for implementing the method of the invention. In this embodiment, the compressor 22 is disposed in the conduit 25 and, upon compression, the recycled gas stream is separated in said separator 24. The advantage of this arrangement is that the volume of compressed gas in said compressor is smaller and thus the compressor may be smaller, this process is optimized and production costs are reduced.

Figure 5 shows another arrangement for carrying out the method according to the invention, in which said compressor 22 is again arranged in a line 25 downstream of said separator 24, but upstream of said second heat exchanger 23 which is located on the separated gas stream path and not upstream of said separator. This arrangement also provides better process optimization.

The process according to the invention will now be illustrated in more detail in the following examples.

DETAILED DESCRIPTION OF THE INVENTION

Examples 1 to 11

Computer simulated examples of gas phase olefin polymerization in a fluidized bed reactor under the conditions of the invention (Examples 1 to 5, 9 and 10) and reference examples of olefin polymerization carried out under conventional conditions without liquid separation in the recycle stream (Examples 6 to 8 and 11).

Examples 1 to 8 represent copolymerizations of ethylene with various alpha-olefins using a conventional Ziegler catalyst, and Examples 9 to 11 represent the homopolymerization of ethylene carried out using a conventional chromium oxide catalyst supported by silica.

Reactor specific power and reactor inlet temperature were calculated using a computer thermal balance program with an accuracy of +15%. For the polymerization system, the dew point temperature and recycle liquid inflow were calculated using a conventional software program to an accuracy of + 10%.

Examples 1, 3, 4 and 10 most accurately represent typical operating conditions for implementing the method of the invention.

The results of the above tests, which are summarized in Table 1 and Table 2, clearly show the increased specific power achievable by the method of the invention.

The term "% of liquid in the recycle stream" in Tables 1 and 2 represents the percentage of the total weight of the liquid recycled by the injection means divided by the total weight of the gas (recycled gas plus all atomizing gas).

Examples 12 to 15

A test apparatus, the arrangement of which is shown in Figure 6, was used to test the fluid feed into the fluidized bed using the described injection means. The test apparatus comprises an aluminum fluid vessel 50 having a retarding zone 56 comprising a polyethylene powder bed 51 (high density or linear low density polyethylene). prepared in advance by gas-phase polymerization of polyethylene in a fluidized bed in an industrial size. Said bed 51 was swirled by a continuously passing stream of dry nitrogen gas fed via line 52 through a preheater 53 to the base chamber 54 of the container 50 and through the grate 55 into said bed. Nitrogen gas is supplied from a commercial liquid nitrogen reservoir, and the amount of nitrogen supplied to swirl said bed and gas pressure in said system were controlled by valves 57 and 69, flow rate being determined using a conventional turbine measuring means (not shown). Said preheater unit had a nominal heating capacity of 72 kW which was controllable to heat nitrogen gas to the desired temperature. The volatile liquid hydrocarbon 58 (1-hexene or n-pentane) was introduced into said fluidised bed 51 from a cooler / demister reservoir 59 by means of a pump 60 and a line 61. The volatile liquid hydrocarbon was introduced into said bed by a nozzle discharge arrangement 62 entering of said bed. Various nozzle discharge arrangements have been tested, some of which are of the liquid type only and others of the gas spray medium type. In the latter type, the atomizing gas was introduced through line 63 (for example, the nozzle shown in Figure 2). The volatile liquid hydrocarbon that entered the fluidized bed via the nozzle discharge arrangement 62 was vaporized in said bed, causing cooling to be absorbed by the latent firing heat. The nitrogen fluidizing gas and the accompanying vaporized liquid hydrocarbon entered from the top of the fluidized bed into said deceleration zone 56, with all the polyethylene powder entrained in said gas stream falling back into said bed. Said gas was then passed to line 64, filter unit 65 and check valve 66, to reservoir 59 and to the deminer. Said cooler / demister container 59 contained two heat exchangers 67, 68. The heat exchanger 67 was cooled by passing cold water and the heat exchanger 68 was cooled by the circulation of cooled ethylene glycol and an aqueous antifreeze solution. Passing said gas through heat exchangers 67, 68 cools said gas and causes condensation of the liquid hydrocarbon (hexene or pentane). The liquefied hydrocarbon was collected in the base reservoir 59 from where it was recycled back to said fluidized bed. Nitrogen gas, thus substantially released from said hydrocarbon, was then introduced through a check valve 69 into the atmosphere. The vortexing and evaporation of said liquid hydrocarbon in said bed was sensed using a commercially available X-ray imaging device including an X-ray source 70. An image amplifier 71 and a CCD video camera 72 whose output has been continuously recorded to a VCR (not shown). The X-ray source, image intensifier and video camera have been mounted on the movable portal 73, which will allow changing the viewing angle as needed in the future.

Said process according to the invention provides a substantial improvement regarding the productivity of the gas phase fluidized bed polymerization processes over existing processes. The process according to the invention can be used in new plants or in existing plants in order to achieve a significant increase in productivity and improved control of the added liquid into said bed. In the case of installing new equipment, capital cost reduction can be achieved by using smaller reaction vessels, compressors and other auxiliary equipment to achieve comparable productivity with respect to the productivity of conventional equipment. In the case of existing equipment, modification of such equipment according to the invention will result in a substantial increase in productivity and improved control of the process.

The test results are summarized in Table 3, wherein Examples 12, 14 and 15 represent the methods of the invention and Example 13 is a comparative example. Example 12 and Comparative Example 13 illustrate the use of the same nozzle arrangement, but in the Comparative Example, the addition of liquid to the "cooled" zone of the gas phase fluidized bed is simulated by operating said bed at 45 ° C compared to 98 ° C used in Example 12. under these conditions, pieces of polymer moistened with a liquid hydrocarbon are formed around said nozzle. Examples 12, 14 and Comparative Example 13 use a spray nozzle liquid with a gaseous spray medium to introduce the liquid of the spray nozzle, and Example 15 uses only a liquid nozzle. In all examples 12, 14 and 15, good dispersion and penetration of the liquid hydrocarbon was achieved, the penetration being stopped only by the wall of the vessel. In Comparative Example 12, liquid penetration is interrupted by the formation of agglomerated pieces of polymer moistened with a liquid hydrocarbon.

SK 281033 Β6

Table 1

C2 / C4 copolymer n © NT CM en CN tn oô CM <M UI ts CN • CN * 4 n tM rr V-4 00 50 ON W4 ABOUT © 5 VJ NT »-4 NT r- CN NT r- < 50 NT ABOUT IN) 5® E U> r O U a o Network 50 CM 50 r * 00 • IN) IN) rM cn RVJ well 09 w TT iri cn o O VO NT cn © N »—C 00 NT NT 50 * 4 50 cn 4 CA NT Ό «E U> * -. - JM O U Cl NT CM CM OO CM en CM ΤΓ ♦ -4 O> · « V) en w cn uô cn en ABOUT 50 and NT © 5 m4 > 4 ~ 00 00 Tr VJ OŇ 50 cn «- < ABOUT 5Z ΓΊ ’Φ in E U> r * ° U a. o 5Z NT <M CM CO · - « ON CM © N «H CN N? «-m CN m · r ^ RR- cn rí O NO and N? m o ** 4 NT en m ABOUT- Ό FM C * 4 and · E U> ω ° For Q. o 1Z Ό <M r *) CN en 04 NT ιη what 50 CN 04 50 <M oô ABOUT »- < NT · -t ABOUT 50 ιη NT m CN pole NO cn CN © Q O · VJ «-Μ (M - k. \ 3) -x E U> **. - rN O U Q. ABOUT 5Z nt 04 m CN and m OO nt 04 NO 04 cn CN 04 ABOUT nt O NO O o and M O NT and 50 NT Cn O r- * T ~ T tJ a 2RT * - a_ 4-a 2C □ 73 ABOUT > - CL Reactor pressure (bar) ABOUT e • s ^ ( « > = o 4> ra ω L. ra * and £ CL-H o E £ a ŕs rH a, J c 5 '»= OJ>» * and p · -p + J S ® ® CL 2> s ? W 2 73 c '' Φ 4-1 3 X) pentane hexene 4-MP1 > ϊ n XD and o ÓC Ή r4 ABOUT Ct • ct X H H and χα Gas velocity (cm / s) z—> Ψ k. + o E > N <O <3 -M 4) > <* N x: <0 E * - ·. cn iZ N — a * ITF UO 4 = 2à and Φ them C o 2tí > ·> C LΦ S 0 Nm * 4Γ U. o 4-a 2d ra Φ ί- α 4 about Q. Φ 4-a ' « C CL 2 44 > at 0 Dew Point Temperature (’C) <v & M Q. E o c ra> o JC>. o φ > > C and Q. 4 ž about*

SK 281033 Β6

Table 2

rh C2 homopolymer 20 103 ΙΛ «Μ / · In · C * ·) in * · * - < - 'CN 4.4 60 14.5 75 57 W) Xr xr 1 ABOUT PJ about C2 homopolyi 24 103 -. _ in V3 cš-Z cš ui «s -« <s 11.2 within XT O VO 14.5 CO r- xo tn 56.3 15.7 σ \ \ a »E> ABOUT C XT CN 103 - <o · iq οχ κό r <<s · -> - · <s 13.3 n xà O XO 14.5 n CX »- < Όνο m rO (N VO CM c o £ L. KQ) WHAT C2 / C4 Kopoiyrr 24 Ό r * “1 r- <n 12 £ c <r- '£ ri to r> 1.25 O Ό 14.5 55 Γζ Οχ xr IN) CO cN ABOUT bi * 'ω r * C2 / C4 Kopoiyrr XT <N XT r * r * m «q U U w S cs CO O vo and χτ 55 50.1 38.2 ABOUT Example Product Reactor pressure (bar) Reactor temperature (’C) o E £ dp * r — 1 O. · MC N CM CM * ^C £ -p -PT? a □ oj and><d> u -Q Ä pentane hexene 4-MP1 hs h 'S s * Ή H 0 • H and> o Gas velocity (cm / s) o> u · 4 * G E * x. > N O (3 A> 0 *>>) Reactor specific power (Kg / m ³ h) Reactor inlet temperature (“C”) U 0 Dew point temperature (“C, in 1T '5 να. E o c «> _o Ä >. o o b. > c Έ CL ' 4 > X £

SK 281033 Β6

Example 12 13 14 15 type of nozzle kvap.-gas liq-gas kvap.-gas kvapäinová type of drain hole 4 horizontal not slits • 4 horizontal slots 4 Horizontal Slots 2 holes with 1.75 mm diameter Area above grate (cm 52 52 10 52 gas spray rate 45 42 52 38 Temp. s (° C) 98 45 78 97 pressure (MPa) 1.01 0.97 0.78 0.75 Bed material HDPE BP 6070 HDPE BP 6070 LLDPE BP 0209 HDPE BP 6070 bed capacity (kg 60 58.5 61.2 58.0 liquid hexene hexthexén n-pentane hexene liquid flow rate (m ^ / h) 1.65 1.48 1.78 0.69 nozzle liquid pressure (MPa) 0.33 0.32 0.38 0.54 atomizing pressure Do not flow * (Ϊρηϊ 0.42 0.40 0.45 it's not spray gas: liquid (wt%) 5.4 5.3 5.6 it's not m ^{J of} liquid per m of bed per hour 11.38 10.61 12.80 4.95 Horizontal, penetration drip. (Cm) over 21 less than 15 more than 21 more than 21 £ condensed chap. {% tot. dropped / total gas 105.5 94.6 121.2 46.6

Claims (32)

A continuous process for the polymerization of an olefin monomer selected from the group consisting of ethylene, propylene, mixtures of propylene and ethylene, and mixtures thereof with at least one other alpha-olefin in the gas phase in a fluidized bed reactor, characterized in that the gas stream comprises ethylene and / or propylene is continuously recycled by the fluidized bed reactor in the presence of a polymerization catalyst under reaction conditions, wherein at least a portion of the gas stream drawn from the reactor is cooled to a temperature at which the condensing liquid is separated. the stream passing through the fluidized bed will substantially reach the temperature of the gaseous stream being withdrawn from the reactor or above. Continuous process according to claim 1, characterized in that the gas stream comprising ethylene and / or propylene is continuously recycled through the fluidized bed in the reactor in the presence of a polymerization catalyst under reaction conditions, wherein at least a portion of the gas stream withdrawn from the reactor is cooled to a temperature at condensation of liquid, at least a part of which is separated and is introduced directly into the fluidized bed by means of at least one part of a liquid nozzle or a spray nozzle with a gaseous spray medium. The continuous process according to any one of the preceding claims, characterized in that at least one further alpha-olefin has 4 to 8 carbon atoms. The continuous process according to any one of the preceding claims, characterized in that the ethylene or propylene is present in an amount which represents at least 70% of all monomers. Continuous process according to one of the preceding claims, characterized in that the cold is cooled. and divides substantially all of the recycled gas stream into the gaseous and liquid portions, with substantially all of the separated liquid being introduced into the reactor. Continuous method according to any one of the preceding claims, characterized in that the liquid is introduced directly into the fluidized bed through a plurality of locations within the bed. Continuous process according to any one of the preceding claims, characterized in that the gas in the fluidized bed is moved at a speed of 50 to 70 cm / s. Continuous process according to any one of the preceding claims, characterized in that the catalyst or prepolymer is introduced into the fluidized bed in a liquefied liquid. Continuous process according to any one of the preceding claims, characterized in that the stream of liquid separated is cooled before being introduced into the fluidized bed. Continuous process according to one of the preceding claims, characterized in that fresh ethylene is introduced into the separated recycled gas stream before it is introduced into the reactor. Continuous process according to one of the preceding claims, characterized in that the liquid is introduced into the fluidized bed at a flow rate of 0.3 to 4.9 m ^{3 of} liquid / 1 m ³ of fluidized bed material / 1 hour. The continuous process according to any one of the preceding claims, characterized in that the weight ratio of liquid to total gas introduced into the fluidized bed is 5: 100 to 85: 100. Continuous process according to claim 12, characterized in that fresh ethylene is used as the atomizing gas. Continuous method according to any one of claims 12 to 13, characterized in that the ratio of the mixing (atomizing) chamber (cm ³ ) / volume of the liquid preceding the chamber (cm ³ / s) is in the range of 5 x 10 ^-3 up to 5 x 10 's. Continuous process according to any one of claims 12 to 14, characterized in that the ratio by weight of the atomizing gas to the pressurized fluid is in the range from 5: 95 to 25: 75. Continuous method according to any one of claims 12 to 15, characterized in that the size of the liquid droplets in the nozzle outlet is in the range of 50 to 4000 µm. Continuous process according to any one of claims 12 to 16, characterized in that the pressure drop in the spray nozzle with the gaseous atomizing medium is in the range from 0.3 MPa to 0.5 MPa and in the case of a liquid nozzle without gaseous atomizing medium from 0.4 to 0.5 MPa. 18. The continuous process of claim 1, wherein the monomer-containing gas stream is continuously recycled through the fluidized bed in the reactor in the presence of a polymerization catalyst under reaction conditions, wherein at least a portion of the gas stream withdrawn from the reactor is cooled to a temperature at at least a portion is subsequently separated and introduced directly into the fluidized bed as one or more separate liquid streams or one or more liquid and gas streams through one or more nozzle outlets located at a point where the gas stream passing through the fluidised bed substantially reaches temperature of the gaseous stream withdrawn from or above the reactor, the individual streams having a horizontal flow momentum of at least 100 x 10 ³ kg.s' ¹ m ' ² .ms' ¹ in the case of a liquid nozzle without gaseous spray medium and pressure liquid the nozzles have a horizontal flow momentum, which is defined as the liquid flow rate (kg / s) in the horizontal direction per unit cross-sectional area (m ² ) of the nozzle outlet from which the liquid is ejected, multiplied by the horizontal velocity component (m / s) of the nozzle; 200 x 10 ³ kg.s ' ^l m' ² .ms · ¹ . The continuous method according to any one of the preceding claims, characterized in that one or more liquid or liquid-gas streams are introduced into the fluidized bed substantially horizontally. Continuous method according to any one of claims 18 to 19, characterized in that one or more liquid or liquid and gas jets are introduced into the fluidized bed through the outlet openings of one or more nozzles. The apparatus for carrying out the method of claim 1, comprising a fluidized bed reactor comprising a reactor body (16) comprising a fluidizing bed (16), a fluidized bed (17) and a velocity retarding zone (18). wherein the fluidized bed (17) is arranged above the fluidizing grid (16); a conduit (19) connecting the reactor to the cyclone (20); a first heat exchanger (21); a compressor (22); a second heat exchanger (23); a separator (24); a conduit (25) for introducing recycled liquid into the reactor body (15), terminated by spray nozzles for injecting the recycled liquid; and a conduit (27) for introducing the catalyst or prepolymer into the liquid separation stream. SK 281033 Β6 Apparatus according to claim 21, characterized in that the spray nozzles are arranged vertically in the fluidized bed (17). Apparatus according to claim 22, characterized in that the spray nozzles are gas-liquid spray nozzles (7) comprising at least one pressurized liquid inlet (13), at least one atomizing gas inlet (12), a mixing chamber (11) for mixing the pressurized liquid and the atomizing gas and at least one discharge opening (10) for discharging the gas-liquid mixture. Apparatus according to claim 23, characterized in that the gas-liquid spray nozzles are provided with more than one discharge opening (10). Apparatus according to claim 24, characterized in that all the outlet openings (10) have a slot configuration. Device according to claim 21, characterized in that the horizontal flow momentum of the current in the liquid nozzle or gas-liquid nozzle is at least 250 x 10 ³ kg · s · ¹ · ² · ms · ·. Apparatus according to claim 21, characterized in that the spray nozzles are equally spaced from one another and separated from the vertical wall of the fluidized bed reactor by the same distance. Apparatus according to claims 21 to 27, characterized in that 1 to 4 spray nozzles are arranged per 10 m ^{2 of the} horizontal cross-sectional area of the fluidized bed (17). Apparatus according to claims 21 to 28, characterized in that each spray nozzle comprises 3 to 16 discharge openings (10). Apparatus according to claim 23, characterized in that each spray nozzle carries a plurality of discharge openings (10) disposed circumferentially of said spray nozzle. Device according to claim 30, characterized in that the spray nozzle discharge openings (10) have a slot configuration. Apparatus according to any one of claims 21 to 31, characterized in that the nozzle is provided with a means for performing emergency gas washing of the nozzle.